Heat exchanger arrangement for hvac systems

ABSTRACT

A multiple circuit refrigerant system includes a first refrigerant circuit having a first condenser and a first compressor. The first compressor is an intermediate discharge valve (IDV) compressor. The multiple circuit refrigerant system also includes a second refrigerant circuit having a second condenser and a second compressor. The second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/724,518, entitled “HEAT EXCHANGER ARRANGEMENT FOR HVAC SYSTEMS,” filed Aug. 29, 2018, which is hereby incorporated by reference in its entirety for all purposes.

BACKGROUND

The present disclosure relates generally to environmental control systems, and more particularly, to a heat exchanger arrangement for heating, ventilation, and/or air conditioning (HVAC) systems having multiple refrigerant circuits.

A wide range of applications exists for HVAC systems. For example, residential, light commercial, commercial, and industrial systems are used to control temperatures and air quality in residences and buildings. Such systems may be dedicated to either heating or cooling, although systems are common that perform both of these functions. Very generally, these systems operate by implementing a thermal cycle in which fluids are heated and cooled to provide the desired temperature in a controlled space, typically the inside of a residence or building. For example, a refrigerant circuit may circulate a refrigerant through one or more heat exchangers to exchange thermal energy between the refrigerant and one or more fluid flows, such as a flow of air. Similar systems are used for vehicle heating and cooling, and as well as for general refrigeration. In some HVAC systems, multiple refrigerant circuits may be used to circulate multiple refrigerant flows that exchange thermal energy with fluid flows in order to condition air that is supplied to a building.

SUMMARY

In one embodiment of the present disclosure, a multiple circuit refrigerant system includes a first refrigerant circuit having a first condenser and a first compressor. The first compressor is an intermediate discharge valve (IDV) compressor. The multiple circuit refrigerant system also includes a second refrigerant circuit having a second condenser and a second compressor. The second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser.

In another embodiment of the present disclosure, a multiple circuit refrigerant system includes a first refrigerant circuit having a first condenser and a first compressor assembly fluidly coupled to the first condenser. The multiple circuit refrigerant system also includes a second refrigerant circuit having a second condenser and a second compressor assembly fluidly coupled to the second condenser. The second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser. Additionally, the first compressor assembly includes a greater quantity of intermediate discharge valve (IDV) compressors than the second compressor assembly.

In a further embodiment of the present disclosure, a multiple circuit refrigerant system includes a first refrigerant circuit having a first condenser and a first compressor. The first compressor is an intermediate discharge valve (IDV) compressor including an IDV. The multiple circuit refrigerant system includes a second refrigerant circuit having a second condenser and a second compressor. The second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser. Additionally, the multiple circuit refrigerant system includes a controller configured to actuate the first compressor in response to a request for part-load operation of the multiple circuit refrigerant system. The first compressor is configured to actuate the IDV during the part-load operation of the multiple circuit refrigerant system.

Other features and advantages of the present application will be apparent from the following, more detailed description of the embodiments, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a commercial or industrial HVAC system, in accordance with an aspect of the present disclosure;

FIG. 2 is a perspective cutaway view of an embodiment of a packaged unit of an HVAC system, in accordance with an aspect of the present disclosure;

FIG. 3 is a perspective cutaway view of an embodiment of a split system of an HVAC system, in accordance with an aspect of the present disclosure;

FIG. 4 is a schematic diagram of an embodiment of a vapor compression system of an HVAC system, in accordance with an aspect of the present disclosure;

FIG. 5 is a schematic diagram of an embodiment of an HVAC system having multiple refrigerant circuits and a serial condenser arrangement, in accordance with an aspect of the present disclosure;

FIG. 6 is a schematic diagram of an embodiment of a serial condenser arrangement for refrigerant circuits having multiple compressors, in accordance with an aspect of the present disclosure;

FIG. 7 is a perspective diagram of an embodiment of a condenser of a serial condenser arrangement for a multiple refrigerant circuit system having two refrigerant circuits, in accordance with an aspect of the present disclosure;

FIG. 8 is a perspective diagram of an embodiment of a condenser of a serial condenser arrangement for a multiple refrigerant circuit system having three refrigerant circuits, in accordance with an aspect of the present disclosure; and

FIG. 9 is a perspective diagram of an embodiment of a condenser of a serial condenser arrangement having a V-shaped configuration, in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed toward a serial condenser arrangement for multiple refrigerant circuit systems that include condenser coils having a serial configuration and one or multiple compressors with intermediate discharge valves (IDVs). As noted herein, multiple refrigerant circuit systems, or multiple circuit refrigerant systems, refer to systems having more than one circuit that each employ any suitable working fluid for performing work. The serial condenser arrangement utilizes a serial configuration in which a first condenser coil of a first refrigerant circuit is disposed upstream of a second condenser coil of a second refrigerant circuit, relative to an air flow directed across the condenser coils. Additionally, the first refrigerant circuit includes a greater quantity of compressors having IDVs, hereinafter IDV compressors, than the second refrigerant circuit. As noted herein, the IDVs within the IDV compressors may open during part-load operations of the multiple refrigerant circuit system to enable the IDV compressors to operate at more efficient operating points. That is, the IDVs may release a refrigerant from an intermediate volume of the IDV compressors, instead of directing the refrigerant to travel through an entire volume of the IDV compressors and become over-compressed relative to the refrigerant downstream of the IDV compressors.

During part-load operation of the multiple refrigerant circuit system having the serial condenser arrangement, the air flow is directed sequentially through the condenser coils in series, such that the air flow is warmed from ambient temperature to a first elevated temperature via contact with the first condenser coil, and then further warmed to a second elevated temperature via contact with the second condenser coil. Simultaneously, a first refrigerant traveling through the first condenser coil is cooled from a first warm inlet temperature to a first cool outlet temperature, and a second refrigerant traveling through the second condenser coil is cooled from a second warm inlet temperature to a second cool outlet temperature. The absolute difference between the first cool outlet temperature and the first warm inlet temperature is referred to herein as a temperature lift of the first condenser coil, and the absolute difference between the second cool outlet temperature and the second warm inlet temperature is referred to herein as a temperature lift of the second condenser coil. In other words, temperature lift refers to a temperature difference between a saturated discharge temperature and a saturated suction temperature for a particular coil.

The serial condenser arrangement disclosed herein may leverage the IDVs of the compressors of the first refrigerant circuit to reduce the temperature lift of the first condenser coil by a greater degree than the temperature lift of the second condenser coil may be increased. Indeed, by lowering the temperature lift of the first condenser coil by a greater degree than the temperature lift of the second condenser coil may be raised, the disclosed serial condenser arrangement efficiently leverages the part-load operating benefits of the IDVs to improve overall operation of the multiple refrigerant circuit system. That is, because temperature lift is generally representative of a compressor ratio for a compressor of the multiple refrigerant circuit system, lowering the temperature lift also reduces the compressor ratio, thereby lowering the compressor power utilized for a same amount of compression work to be performed.

Accordingly, the serial condenser arrangement may lower the temperature lift for the refrigerant circuit having the upstream condenser coil, lower specific compressor work, and accordingly increase a coefficient of performance and an efficiency of the refrigerant circuit by a greater degree than the corresponding efficiency of the downstream condenser coil and second refrigerant circuit are decreased. The serial condenser arrangement thereby improves overall operation of the HVAC system, compared to traditional HVAC systems without the disclosed serial condenser arrangement.

Turning now to the drawings, FIG. 1 illustrates an embodiment of a heating, ventilation, and/or air conditioning (HVAC) system for environmental management that may employ one or more HVAC units. As used herein, an HVAC system includes any number of components configured to enable regulation of parameters related to climate characteristics, such as temperature, humidity, air flow, pressure, air quality, and so forth. For example, an “HVAC system” as used herein is defined as conventionally understood and as further described herein. Components or parts of an “HVAC system” may include, but are not limited to, all, some of, or individual parts such as a heat exchanger, a heater, an air flow control device, such as a fan, a sensor configured to detect a climate characteristic or operating parameter, a filter, a control device configured to regulate operation of an HVAC system component, a component configured to enable regulation of climate characteristics, or a combination thereof. An “HVAC system” is a system configured to provide such functions as heating, cooling, ventilation, dehumidification, pressurization, refrigeration, filtration, or any combination thereof. The embodiments described herein may be utilized in a variety of applications to control climate characteristics, such as residential, commercial, industrial, transportation, or other applications where climate control is desired.

In the illustrated embodiment, a building 10 is air conditioned by a system that includes an HVAC unit 12. The building 10 may be a commercial structure or a residential structure. As shown, the HVAC unit 12 is disposed on the roof of the building 10; however, the HVAC unit 12 may be located in other equipment rooms or areas adjacent the building 10. The HVAC unit 12 may be a single package unit containing other equipment, such as a blower, integrated air handler, and/or auxiliary heating unit. In other embodiments, the HVAC unit 12 may be part of a split HVAC system, such as the system shown in FIG. 3, which includes an outdoor HVAC unit 58 and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building 10. Specifically, the HVAC unit 12 may include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unit 12 is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and/or a return air flow from the building 10. After the HVAC unit 12 conditions the air, the air is supplied to the building 10 via ductwork 14 extending throughout the building 10 from the HVAC unit 12. For example, the ductwork 14 may extend to various individual floors or other sections of the building 10. In certain embodiments, the HVAC unit 12 may be a heat pump that provides both heating and cooling to the building with one refrigeration circuit configured to operate in different modes. In other embodiments, the HVAC unit 12 may include one or more refrigeration circuits for cooling an air stream and a furnace for heating the air stream.

A control device 16, one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device 16 also may be used to control the flow of air through the ductwork 14. For example, the control device 16 may be used to regulate operation of one or more components of the HVAC unit 12 or other components, such as dampers and fans, within the building 10 that may control flow of air through and/or from the ductwork 14. In some embodiments, other devices may be included in the system, such as pressure and/or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control device 16 may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. In the illustrated embodiment, the HVAC unit 12 is a single package unit that may include one or more independent refrigeration circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit 12 may provide a variety of heating and/or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unit 12 may directly cool and/or heat an air stream provided to the building 10 to condition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2, a cabinet 24 encloses the HVAC unit 12 and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet 24 may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails 26 may be joined to the bottom perimeter of the cabinet 24 and provide a foundation for the HVAC unit 12. In certain embodiments, the rails 26 may provide access for a forklift and/or overhead rigging to facilitate installation and/or removal of the HVAC unit 12. In some embodiments, the rails 26 may fit into “curbs” on the roof to enable the HVAC unit 12 to provide air to the ductwork 14 from the bottom of the HVAC unit 12 while blocking elements such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluid communication with one or more refrigeration circuits. Tubes within the heat exchangers 28 and 30 may circulate refrigerant, such as R-410A, through the heat exchangers 28 and 30. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers 28 and 30 may implement a thermal cycle in which the refrigerant undergoes phase changes and/or temperature changes as it flows through the heat exchangers 28 and 30 to produce heated and/or cooled air. For example, the heat exchanger 28 may function as a condenser where heat is released from the refrigerant to ambient air, and the heat exchanger 30 may function as an evaporator where the refrigerant absorbs heat to cool an air stream. In other embodiments, the HVAC unit 12 may operate in a heat pump mode where the roles of the heat exchangers 28 and 30 may be reversed. That is, the heat exchanger 28 may function as an evaporator and the heat exchanger 30 may function as a condenser. In further embodiments, the HVAC unit 12 may include a furnace for heating the air stream that is supplied to the building 10. While the illustrated embodiment of FIG. 2 shows the HVAC unit 12 having two of the heat exchangers 28 and 30, in other embodiments, the HVAC unit 12 may include one heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separates the heat exchanger 30 from the heat exchanger 28. Fans 32 draw air from the environment through the heat exchanger 28. Air may be heated and/or cooled as the air flows through the heat exchanger 28 before being released back to the environment surrounding the rooftop unit 12. A blower assembly 34, powered by a motor 36, draws air through the heat exchanger 30 to heat or cool the air. The heated or cooled air may be directed to the building 10 by the ductwork 14, which may be connected to the HVAC unit 12. Before flowing through the heat exchanger 30, the conditioned air flows through one or more filters 38 that may remove particulates and contaminants from the air. In certain embodiments, the filters 38 may be disposed on the air intake side of the heat exchanger 30 to prevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing the thermal cycle. Compressors 42 increase the pressure and temperature of the refrigerant before the refrigerant enters the heat exchanger 28. The compressors 42 may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors 42 may include a pair of hermetic direct drive compressors arranged in a dual stage configuration 44. However, in other embodiments, any number of the compressors 42 may be provided to achieve various stages of heating and/or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit 12, such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things.

The HVAC unit 12 may receive power through a terminal block 46. For example, a high voltage power source may be connected to the terminal block 46 to power the equipment. The operation of the HVAC unit 12 may be governed or regulated by a control board 48. The control board 48 may include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device 16. The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring 49 may connect the control board 48 and the terminal block 46 to the equipment of the HVAC unit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also in accordance with present techniques. The residential heating and cooling system 50 may provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling system 50 is a split HVAC system. In general, a residence 52 conditioned by a split HVAC system may include refrigerant conduits 54 that operatively couple the indoor unit 56 to the outdoor unit 58. The indoor unit 56 may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit 58 is typically situated adjacent to a side of residence 52 and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The refrigerant conduits 54 transfer refrigerant between the indoor unit 56 and the outdoor unit 58, typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, a heat exchanger 60 in the outdoor unit 58 serves as a condenser for re-condensing vaporized refrigerant flowing from the indoor unit 56 to the outdoor unit 58 via one of the refrigerant conduits 54. In these applications, a heat exchanger 62 of the indoor unit functions as an evaporator. Specifically, the heat exchanger 62 receives liquid refrigerant, which may be expanded by an expansion device, and evaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger 60 using a fan 64 and expels the air above the outdoor unit 58. When operating as an air conditioner, the air is heated by the heat exchanger 60 within the outdoor unit 58 and exits the unit at a temperature higher than it entered. The indoor unit 56 includes a blower or fan 66 that directs air through or across the indoor heat exchanger 62, where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork 68 that directs the air to the residence 52. The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence 52 is higher than the set point on the thermostat, or a set point plus a small amount, the residential heating and cooling system 50 may become operative to refrigerate additional air for circulation through the residence 52. When the temperature reaches the set point, or a set point minus a small amount, the residential heating and cooling system 50 may stop the refrigeration cycle temporarily.

The residential heating and cooling system 50 may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers 60 and 62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58 will serve as an evaporator to evaporate refrigerant and thereby cool air entering the outdoor unit 58 as the air passes over outdoor the heat exchanger 60. The indoor heat exchanger 62 will receive a stream of air blown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70. For example, the indoor unit 56 may include the furnace system 70 when the residential heating and cooling system 50 is not configured to operate as a heat pump. The furnace system 70 may include a burner assembly and heat exchanger, among other components, inside the indoor unit 56. Fuel is provided to the burner assembly of the furnace 70 where it is mixed with air and combusted to form combustion products. The combustion products may pass through tubes or piping in a heat exchanger, separate from heat exchanger 62, such that air directed by the blower 66 passes over the tubes or pipes and extracts heat from the combustion products. The heated air may then be routed from the furnace system 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can be used in any of the systems described above. The vapor compression system 72 may circulate a refrigerant through a circuit starting with a compressor 74. The circuit may also include a condenser 76, an expansion valve(s) or device(s) 78, and an evaporator 80. The vapor compression system 72 may further include a control panel 82 that has an analog to digital (A/D) converter 84, a microprocessor 86, a non-volatile memory 88, and/or an interface board 90. The control panel 82 and its components may function to regulate operation of the vapor compression system 72 based on feedback from an operator, from sensors of the vapor compression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or more of a variable speed drive (VSDs) 92, a motor 94, the compressor 74, the condenser 76, the expansion valve or device 78, and/or the evaporator 80. The motor 94 may drive the compressor 74 and may be powered by the variable speed drive (VSD) 92. The VSD 92 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 94. In other embodiments, the motor 94 may be powered directly from an AC or direct current (DC) power source. The motor 94 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.

The compressor 74 compresses a refrigerant vapor and delivers the vapor to the condenser 76 through a discharge passage. In some embodiments, the compressor 74 may be a centrifugal compressor. The refrigerant vapor delivered by the compressor 74 to the condenser 76 may transfer heat to a fluid passing across the condenser 76, such as ambient or environmental air 96. The refrigerant vapor may condense to a refrigerant liquid in the condenser 76 as a result of thermal heat transfer with the environmental air 96. The liquid refrigerant from the condenser 76 may flow through the expansion device 78 to the evaporator 80.

The liquid refrigerant delivered to the evaporator 80 may absorb heat from another air stream, such as a supply air stream 98 provided to the building 10 or the residence 52. For example, the supply air stream 98 may include ambient or environmental air, return air from a building, or a combination of the two. The liquid refrigerant in the evaporator 80 may undergo a phase change from the liquid refrigerant to a refrigerant vapor. In this manner, the evaporator 80 may reduce the temperature of the supply air stream 98 via thermal heat transfer with the refrigerant. Thereafter, the vapor refrigerant exits the evaporator 80 and returns to the compressor 74 by a suction line to complete the cycle.

In some embodiments, the vapor compression system 72 may further include a reheat coil in addition to the evaporator 80. For example, the reheat coil may be positioned downstream of the evaporator relative to the supply air stream 98 and may reheat the supply air stream 98 when the supply air stream 98 is overcooled to remove humidity from the supply air stream 98 before the supply air stream 98 is directed to the building 10 or the residence 52.

It should be appreciated that any of the features described herein may be incorporated with the HVAC unit 12, the residential heating and cooling system 50, or other HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications.

Moreover, in accordance with the present techniques, a serial condenser arrangement or row split condenser arrangement may be utilized within any of the HVAC systems illustrated in FIGS. 1-4. For example, the serial condenser arrangement may be employed within the heat exchanger 28 of the HVAC unit 12 of FIG. 2, the heat exchanger 60 of the residential heating and cooling system 50, the condenser 76 of the vapor compression system 72, and/or any other suitable condenser of an HVAC system having two or more than two refrigerant circuits. That is, the serial condenser arrangement may be provided for the condenser of any suitable multiple refrigerant circuit system, which is collectively referred to as a multiple refrigerant circuit system 100 or HVAC system. Additionally, although discussed herein with reference to a condenser, it is to be understood that the serial condenser arrangement may also be utilized for an outdoor heat exchanger of a heat pump system in which the outdoor heat exchanger may operate as either a condenser or an evaporator. Accordingly, as discussed herein, the serial condenser arrangement having condenser coils in series relative to an air flow across the condenser coils enables the multiple refrigerant circuit system 100 to leverage a part-load operating efficiency accorded by IDVs of an IDV compressor fluidly coupled to an upstream condenser coil. Thus, the upstream condenser coil may operate at a reduced temperature lift and an increased operating efficiency to an increase an overall operating efficiency for the multiple refrigerant circuit system 100. The serial condenser arrangement will be described in more detail below with reference to FIGS. 5-9.

FIG. 5 is a schematic diagram of the multiple refrigerant circuit system 100 having a serial condenser arrangement 102 for a serial condenser 104, in accordance with the present techniques. The multiple refrigerant circuit system 100 includes a first refrigerant circuit 110 in which a first refrigerant 112 flows between a first condenser coil 114, or condenser, of the serial condenser 104 and a first evaporator coil 116 of an evaporator 118. Additionally, the multiple refrigerant circuit system 100 includes a second refrigerant circuit 120 in which a second refrigerant 122 flows between a second condenser coil 124, or condenser, of the serial condenser 104 and a second evaporator coil 126 of the evaporator 118. The first refrigerant 112 and the second refrigerant 122 may each include a same or similar refrigerant. Moreover, the first refrigerant 112 and the second refrigerant 122 may be fluidly and/or thermally isolated or separated from one another, in some embodiments.

As illustrated, the first condenser coil 114 of the first refrigerant circuit 110 is in a serial configuration or row split configuration with the second condenser coil 124 of the second refrigerant circuit 120. More particularly, the first condenser coil 114 may include tubing or a first tube row 130 that is directly adjacent or longitudinally adjacent to tubing or a second tube row 132 of the second condenser coil 124. As such, the first condenser coil 114 may define a first partial coil depth 134 or width of the serial condenser 104 extending along an x-axis 136, while the second condenser coil 124 may define a second partial coil depth 138 of the serial condenser 104 defined along the x-axis 136. A coil depth 140 or complete depth of the serial condenser 104 is therefore cooperatively defined by both the first partial coil depth 134 and the second partial coil depth 138. As referred to herein, the depths of the serial condenser 104 are defined with reference to a direction in which an air flow 150 is directed over, is drawn through, or otherwise passes across the serial condenser 104. Additionally, the serial condenser 104 includes a coil height 152 extending along a y-axis 154, as well as a coil length extending into the illustrated page along a z-axis 156.

Thus, in contrast to a side-by-side condenser that has condenser coils arranged in parallel with one another relative to an air flow through the condenser coils, the first condenser coil 114 and the second condenser coil 124 are separated along a plane generally defined by the y-axis 154 and the z-axis 156. For example, the first condenser coil 114 may include an outward-facing surface 160 and an inward-facing surface 162 that is opposite of the outward-facing surface 160, while the second condenser coil 124 may include an outward-facing surface 164 and an inward-facing surface 166 that is opposite of the outward-facing surface 164. The inward-facing surfaces 162, 166 of the condenser coils 114, 124 may be longitudinally inward relative to each other and/or relative to a vertical centerline 170 of the serial condenser 104 extending along the y-axis 154. Thus, the inward-facing surfaces 162, 166 face one another, and in some embodiments, may be in contact with one another. As such, the air flow 150 drawn across the serial condenser 104 by a blower or fan may flow sequentially through the first condenser coil 114 and then second condenser coil 124 in series, with substantially no air bypass. In other words, the air flow 150 may contact each condenser coil 114, 124 when flowing along the x-axis 136. As referred to herein, the serial condenser 104 includes a stacked slab configuration in which the first condenser coil 114 is upstream of the second condenser coil 124 relative to the air flow 150. Moreover, although presently illustrated with reference to a generally rectangular or slab-shaped condenser, it is to be understood that that the serial condenser arrangement 102 may be extended to any suitable condensers, such as those having a V-shape configuration, an N-shape configuration, a W-shape configuration, and so forth.

After exiting the first condenser coil 114, the first refrigerant 112 is directed through a first expansion valve 172 and then into the first evaporator coil 116. Similarly, after exiting the second condenser coil 124, the second refrigerant 122 is directed through a second expansion valve 174 and then into the second evaporator coil 126. The first evaporator coil 116 and the second evaporator coil 126 may have any suitable configuration, such as an illustrated parallel configuration 180 in which the evaporator coils 116, 126 contact an air flow 182 directed across the evaporator 118 in parallel with one another. In other embodiments, the evaporator 118 may have another suitable configuration, such as a row split configuration or an interlaced coil configuration.

Moreover, fluidly coupled downstream of the evaporator 118, the multiple refrigerant circuit system 100 includes a first compressor 190 that receives, compresses, and provides the first refrigerant 112 to the first condenser coil 114 and a second compressor 192 that receives, compresses, and provides the second refrigerant 122 to the second condenser coil 124. In some embodiments, the compressors 190, 192 have a compressor tonnage suitable for conditioning the interior space of the building 10. The compressor tonnage of each compressor 190, 192 is generally equal to the compressor tonnage of the other compressor 190, 192, such as tonnages within 10 percent of one another, although the compressors 190, 192 may have compressor tonnages that are different from one another in other embodiments. Moreover, it is to be understood that the compressor tonnages discussed herein are nominal, rated compressor tonnages that the compressors 190, 192 are rated or manufactured to produce.

As noted herein, the first compressor 190 includes one or multiple IDVs 194. The IDVs 194 may enable the first compressor 190 to adjust the compression of the first refrigerant 112 based on varying load requirements of the multiple refrigerant circuit system 100. The first compressor 190 may be any suitable scroll compressor having IDV capability, also referred to herein as an IDV compressor. For example, the first compressor 190 may be a scroll compressor having a housing with two interleaving scrolls therein that rotate together to pressurize and/or compress the first refrigerant 112. The IDVs 194 maybe disposed between certain gas pockets formed by the interleaving scrolls and an upper shell or high pressure zone of the first compressor 190. As such, the IDVs 194 may open in response to a pressure differential to bleed off or reduce the pressure of the first refrigerant 112 at part-load operation of the multiple refrigerant circuit system 100, thereby reducing the compressor power utilized. Moreover, the first condenser coil 114 may operate at a lower, more efficient condensing pressure and a reduced temperature lift. During full-load operation of the multiple refrigerant circuit system 100, the IDVs 194 of the first compressor 190 remain closed to enable the first compressor 190 to pressurize the first refrigerant 112 to a greater, or maximum, discharge pressure.

In contrast, during part-load operation of a scroll compressor without IDVs, the scroll compressor may pressurize a refrigerant beyond a pressure set point, such that a pressure of the refrigerant within final gas pockets between interleaving scrolls of the scroll compressor is higher than a pressure of the refrigerant within an upper shell or high pressure zone of the scroll compressor. As such, energy exerted to over-pressurize the refrigerant may contribute to a decrease in efficiency and an increase in power consumption of the traditional scroll compressor.

Notably, the second compressor 192 of the multiple refrigerant circuit system 100 does not include the IDVs 194 and/or the IDV capability present within the first compressor 190. As such, the first refrigerant circuit 110 includes a greater quantity of IDV compressors than the second refrigerant circuit 120. However, as discussed with reference to FIG. 6 below, the second refrigerant circuit 120 may include one or multiple IDV compressors in some embodiments, provided the first refrigerant circuit 110 includes a greater number of IDV compressors.

As recognized herein, by positioning the first condenser coil 114 upstream of the second condenser coil 124 relative to the flow direction of air flow 150, and by including a greater quantity of IDV compressors within the first refrigerant circuit 110 than the second refrigerant circuit 120, the serial condenser arrangement 102 of the multiple refrigerant circuit system 100 may leverage the IDV capability of the first compressor 190 to improve the part-load operating efficiency of the multiple refrigerant circuit system 100. By way of an example, a controller 200 of the multiple refrigerant circuit system 100 may be communicatively coupled to the compressors 190, 192. The controller 200 may therefore operate each compressor 190, 192 based on a cooling load of the interior space of the building 10 to be met by the air flow 182 drawn across the evaporator 118. The controller 200 may include a processor 202, such as the microprocessor 86 discussed above, and a memory 204, such as the non-volatile memory 88 discussed above, to enable the controller 200 to analyze the operating parameters of the serial condenser arrangement 102 and/or the multiple refrigerant circuit system 100.

During a part-load operation of the multiple refrigerant circuit system 100, such as operation at 20 percent, 40 percent, 60 percent, 80 percent, and so forth of a maximum cooling capacity of the multiple refrigerant circuit system 100, the controller 200 may instruct both compressors 190, 192 to operate. Thus, by having the first condenser coil 114 upstream of the second condenser coil 124, the air flow 150 drawn across the serial condenser 104 contacts the first condenser coil 114 when the air flow 150 is at an ambient temperature or condenser inlet temperature, which may correspond to a coolest or lowest temperature of the air flow 150. To cool and condense the first refrigerant 112 within the first condenser coil 114, the first refrigerant 112 may exchange heat with the air flow 150 to warm the air flow 150 to an intermediate temperature that is higher than the ambient temperature, before the air flow 150 is provided to the second condenser coil 124. Then, to cool and condense the second refrigerant 122 within the second condenser coil 124, the second refrigerant 122 may exchange heat with the air flow 150 to warm the air flow 150 from the intermediate temperature to a condenser outlet temperature that is higher than both the intermediate temperature and the ambient temperature.

In particular, because the first condenser coil 114 of the serial condenser arrangement 102 receives the air flow 150 having the relatively cool, ambient temperature, a condensing temperature of the refrigerant 112 within the first condenser coil 114 may be lower than a condensing temperature of the refrigerant 122 within the second condenser coil 124. As such, operation of the first compressor 190 may utilize less compressive work than the second compressor 192 to condense refrigerant, thereby improving an operating efficiency of the first compressor 190. Indeed, based on the IDVs 194 of the first compressor 190, an increase in efficiency provided by the placement of the first condenser coil 114 upstream of the second condenser coil 124 may outweigh any corresponding controlled or intentional decrease in efficiency of the second compressor 192, such as a controlled degradation in efficiency from using the warmer, intermediate temperature of the air flow 150 from the first condenser coil 114 to absorb heat from the second refrigerant 122. In other words, although the second condenser coil 124 may operate at a lower efficiency than a condenser coil that receives an air flow at a relatively cooler, ambient temperature, the part-load operational increase in efficiency from the IDV capability of the first compressor 190 generally outweighs any corresponding decrease in efficiency of the second condenser coil 124, thereby enabling the multiple refrigerant circuit system 100 to operate at an improved overall efficiency.

Additionally, the controller 200 may selectively operate the compressors 190, 192, and the IDVs 194 of the first compressor 190 may selectively self-actuate, based on a current operating load of the multiple refrigerant circuit system 100. For example, during full-load operation of the multiple refrigerant circuit system 100, the controller 200 may operate both compressors 190, 192, the IDVs 194 of the first compressor 190 may remain closed to enable the first compressor 190 to achieve a target operating pressure for the first refrigerant 112, and the air flow 150 may be drawn across each condenser coil 114, 124. During a lower load operation of the multiple refrigerant circuit system 100 in which the controller 200 determines that operation of only one refrigerant circuit is desired, the controller 200 may prioritize operation of the first refrigerant circuit 110 to enable the first compressor 190 to employ the IDVs 194 to selectively adjust the compression of the first refrigerant 112 according to the current operating load of the multiple refrigerant circuit system 100. Moreover, although the air flow 150 may be also drawn across the second condenser coil 124 that does not have the second refrigerant 122 flowing therein because the second refrigerant circuit 120 is not operational, any increase in pressure drop from drawing the air flow 150 across the two condenser coils 114, 124 instead of one condenser coil may be negligible or otherwise may not significantly affect operation of the multiple refrigerant circuit system 100. Indeed, in some embodiments, the coil depth 140 of the serial condenser 104 is the same or similar as a condenser depth of a traditional condenser having side-by-side condenser coils, such that the first partial coil depth 134 and the second partial coil depth 138 are each half as large as a corresponding coil depth of the traditional condenser. In certain embodiments, the coil length of the serial condenser 104 defined along the z-axis 156 is longer than, or twice as long as, a corresponding coil length of the traditional condenser to provide adequate surface area for heat transfer.

In some embodiments, the multiple refrigerant circuit system 100 may also include sensors 210 communicatively coupled to the controller 200 to monitor operating parameters of the multiple refrigerant circuit system 100 and the serial condenser arrangement 102 therein. For example, a first refrigerant sensor 212 may be communicatively coupled to the first condenser coil 114 to monitor properties of the first refrigerant 112 therein, while a second refrigerant sensor 214 may be communicatively coupled to the second condenser coil 124 to monitor properties of the second refrigerant 122 therein. Additionally, the sensors 210 may include a first air flow sensor 216 or ambient air sensor disposed within the multiple refrigerant circuit system 100 to monitor operating parameters of the air flow 150 upstream of the first condenser coil 114, a second air flow sensor 218 to monitor operating parameters of the air flow 150 between the two condenser coils 114, 124, and/or a third air flow sensor 220 to monitor operating parameters of the air flow 150 downstream of the second condenser coil 124. The sensors 210 may be any suitable sensors that enable the controller 200 to monitor any suitable operating parameters of the multiple refrigerant circuit system 100. For example, the operating parameters sensed by the sensors 210 may include temperatures, pressures, flow rates, and so forth of the refrigerants 112, 122 and/or the air flow 150. As such, the sensors 210 may be any suitable sensors for monitoring parameters of the air flow 150 and/or the refrigerants 112, 122 directly or indirectly, such as temperature sensors, pressure sensors, flowrate sensors, and so forth. Moreover, as used herein, the term “sensor” may include any suitable instrument configured to acquire feedback through direct or indirect observation indicators.

As such, the controller 200 may receive and analyze signals from the sensors 210 to enable the controller 200 to determine and monitor the respective performance of each refrigerant circuit 110, 120. In some embodiments, the controller 200 may construct a model or a holistic, comprehensive snapshot of the operating parameters of the serial condenser 104 to enable the controller 200 to identify components and/or operating parameter set points for components. The controller 200 or a technician may adjust operation of the identified components and/or operating parameter set points to further increase the operating efficiency of the multiple refrigerant circuit system 100.

FIG. 6 is an embodiment of the multiple refrigerant circuit system 100 having the serial condenser arrangement 102 with two compressors in each refrigerant circuit 110, 120. More particularly, the first refrigerant circuit 110 includes a third compressor 250 arranged in parallel with the first compressor 190, and the second refrigerant circuit 120 includes a fourth compressor 252 arranged in parallel with the second compressor 192. The compressors 190, 250 of the first refrigerant circuit 110 may be referred to as a first compressor assembly 254, and the compressors 192, 252 of the second refrigerant circuit 120 may be referred to as a second compressor assembly 256. The compressor assemblies 254, 256 may each include any suitable quantity of compressors coupled together in any suitable arrangement. As recognized herein, operational improvements to the multiple refrigerant circuit system 100 may be achieved by leveraging a position of the first condenser coil 114 upstream of the second condenser coil 124 relative to a flow direction of the air flow 150 therethrough, provided that the first refrigerant circuit 110 having the first condenser coil 114 includes a greater number of IDV compressors than the second refrigerant circuit 120 having the second condenser coil 124.

That is, in the present embodiment and as noted above, the first compressor 190 is an IDV compressor having the IDVs 194, while the remaining compressors 192, 250, 252 are each non-IDV compressors. However, in other embodiments, the first and third compressors 190, 250 may each be IDV compressors, while the second and fourth compressors 192, 252 may each be non-IDV compressors. Moreover, in some embodiments, the first, second, and third compressors 190, 192, 250 may each be IDV compressors, while the fourth compressor 252 may be a non-IDV compressor. In other words, any suitable arrangement of the condenser coils 114, 124 and the compressors 190, 192, 250, 252 may be employed, such that one or more than one upstream condenser coil is coupled to a greater number of IDV compressors than one or more than one downstream condenser coil. Additionally, the compressors 190, 192, 250, 252 may each be communicatively coupled to the controller 200 to receive actuation signals therefrom. During part-load operation, the controller 200 may selectively operate each compressor 190, 192, 250, 252 in any suitable order, leveraging the increased part-load operating efficiency of the IDV compressors relative to the decreased part-load operating efficiency of the non-IDV compressors to improve the overall operation of the multiple refrigerant circuit system 100. Moreover, as discussed in more detail with reference to FIG. 8 below, the present techniques may be extended to embodiments of the multiple refrigerant circuit system 100 having any suitable number of refrigerant circuits.

Looking next to more details of the serial condenser arrangement 102, FIG. 7 is a perspective view of the serial condenser 104 having the first condenser coil 114 and the second condenser coil 124. As discussed above, the first condenser coil 114 receives the first refrigerant 112 from the first compressor 190, which is an IDV compressor having the IDVs 194, while the second condenser coil 124 receives the second refrigerant 122 from the second compressor 192, which is a non-IDV compressor. The first condenser coil 114 is upstream of the second condenser coil 124 relative to the air flow 150 to enable the first compressor 190 to utilize the IDV capability of the first compressors 190 to lower the condensing temperature of the first condenser coil 114 relative to the second condenser coil 124 during part-load operation of the multiple refrigerant circuit system 100.

The illustrated serial condenser 104 includes the coil depth 140 extending along the x-axis 136, the coil height 152 extending along the y-axis 154, and a coil length 300 extending along the z-axis 156. As illustrated, the serial condenser 104 includes a separation or split between the first condenser coil 114 and the second condenser coil 124, as defined by a plane extending between the y-axis 154 and the z-axis 156. That is, the first condenser coil 114 includes tube rows that extend along the z-axis 156 in a generally parallel orientation to tube rows of the second condenser coil 124. As discussed herein, generally parallel tube rows refer to tube rows extending along a same direction within 5 percent, 10 percent, 15 percent, and so forth from one another. Moreover, although referred to herein as the serial condenser 104 having generally rectangular condenser coils, it is to be understood that the serial condenser 104 may be formed in any suitable shape, including that of V-shaped condenser coils as illustrated in FIG. 9, a curved outside unit or residential outdoor condenser coil, and so forth. In such embodiments, the serial condenser arrangement 102 may include a first coil stacked or nested within or underneath a second coil, such that a fan may draw an air flow across the second coil and the first coil in series or sequentially.

More particularly and as illustrated, the first condenser coil 114 may include the first tube row 130, and second condenser coil 124 may include the second tube row 132, adjacent to the first tube row 130. Additionally, each coil may include multiple tube rows. For example, as illustrated by a tube arrangement 302, the first condenser coil 114 may additionally include a third tube row 304, and the second condenser coil 124 may additionally include a fourth tube row 306, such that each condenser coil 114, 124 includes two tube rows 130, 132, 304, 306. The tube rows 130, 132, 304, 306 may each generally define a serpentine path 310 extending along the coil length 300 and the coil height 152 of the serial condenser 104. In some embodiments in which the serial condenser 104 is a plate-fin heat exchanger, first heat exchange fins may thermally couple the first tube row 130 and the third tube row 304, which may each carry the first refrigerant 112 therein, while second heat exchange fins thermally couple the second tube row 132 and the fourth tube row 306, which may each carry the second refrigerant 122 therein. It is to be understood that the serial condenser 104 may include any suitable quantity of tube rows within any suitable number of condenser coils, such that a desired amount or level of condensing is performed for each refrigerant circuit 110, 120.

In some embodiments, the first condenser coil 114 and the second condenser coil 124 are manufactured as a unitary or connected unit having a shared structural element. The shared structural element may be any suitable structural component, such as a tubesheet 312 supporting tubes of the tube rows 130, 132, 304, 306 of the condenser coils 114, 124 and/or a housing 314 or enclosure extending around the condenser coils 114, 124. In embodiments in which the serial condenser 104 is a plate-fin heat exchanger formed as a unitary unit, a conductive break or notch 316 may be formed between the first condenser coil 114 and the second condenser coil 124 to block or eliminate cross-conduction of thermal energy between the first refrigerant 112 and the second refrigerant 122. The notch 316 may be a portion of the serial condenser 104 without heat transfer fins. The notch 316 may be formed during or after construction of the serial condenser 104. In embodiments in which the serial condenser 104 is formed as a unitary unit, construction costs for the serial condenser 104 may be reduced compared to embodiments in which the condenser coils 114, 124 are formed separately and then disposed or coupled together thereafter. The serial condenser arrangement 102 may be extended to other types of heat exchangers as well, such as microchannel heat exchangers.

Because the air flow 150 travels across the serial condenser 104 along the x-axis 136, the air flow 150 may contact each tube row 130, 132, 304, 306 of the serial condenser 104 in series, in some embodiments. In this manner, when one or both of the compressors 190, 192 are activated, the air flow 150 traveling across the serial condenser 104 passes over the tubing therein to exchange heat with or remove heat from the corresponding flowing refrigerant 112, 122 within the active condenser coils 114, 124. Thus, because the air flow 150 is colder when entering the first condenser coil 114 than the second condenser coil 124, the serial condenser arrangement 102 may leverage the IDVs 194 of the first compressor 190 during part-load operations to reduce the temperature lift and increase the efficiency of the first refrigerant circuit 110 by a greater degree than a corresponding decrease in efficiency of the second refrigerant circuit 120, thereby improving overall performance of the multiple refrigerant circuit system 100.

FIG. 8 is a perspective view of an embodiment of the serial condenser arrangement 102 for the multiple refrigerant circuit system 100 having three refrigerant circuits. That is, the serial condenser 104 includes the first condenser coil 114 of the first refrigerant circuit 110, the second condenser coil 124 of the second refrigerant circuit 120, and a third condenser coil 350 of a third refrigerant circuit 352. Relative to the air flow 150 across the serial condenser 104, the first condenser coil 114 is upstream of the second condenser coil 124, and the second condenser coil 124 is upstream of the third condenser coil 350. Accordingly, the air flow 150 may be sequentially drawn across the first condenser coil 114, the second condenser coil 124, and the third condenser coil 350. Additionally, the first compressor 190 provides the first refrigerant 112 to the first condenser coil 114, the second compressor 192 provides the second refrigerant 122 to the second condenser coil 124, and a third compressor 354 provides a third refrigerant 356 to the third condenser coil 350.

In general, upstream condenser coils of the serial condenser arrangement 102, relative to the air flow 150, receive refrigerant from a greater quantity of IDV compressors than downstream condenser coils. For example, in the present embodiment, the first compressor 190 is an IDV compressor having the IDVs 194, while the second and the third compressors 192, 354 are non-IDV compressors. However, in other embodiments, the first compressor 190 and the second compressor 192 may be IDV compressors while the third compressor 354 may be a non-IDV compressor. Further, although illustrated with each refrigerant circuit 110, 120, 352 having one compressor, it is to be understood that the serial condenser arrangement 102 may be utilized with refrigerant circuits with some or all refrigerant circuits having multiple compressors. For example, the first condenser coil 114 may receive the first refrigerant 112 from two IDV compressors, the second condenser coil 124 may receive the second refrigerant 122 from one IDV compressor and one non-IDV compressor, and the third condenser coil 350 may receive the third refrigerant 356 from two non-IDV compressors. In other embodiments, the second condenser coil 124 may alternatively receive the second refrigerant 122 from two IDV compressors, while the third condenser coil 350 receives the third refrigerant 356 from one IDV compressor and one non-IDV compressor, or from two non-IDV compressors. As such, the upstream condenser coils receive the air flow 150 at a lower temperature than the downstream condenser coils, thus leveraging the part-load efficiency benefits of the IDV technology to lower the condensing temperature of the upstream condenser coils and improve the overall efficiency of the multiple refrigerant circuit system 100.

FIG. 9 is a perspective diagram of the serial condenser arrangement 102 having serial condenser 104 with a V-shape configuration 380. In the present embodiment, the serial condenser 104 includes a first slab portion 382 disposed at an angle 384, such as 15 degrees, 30 degrees, 45 degrees, and so forth, relative to a second slab portion 386. Each slab portion 382, 386 may receive the air flow 150 therethrough as an upward flow. As illustrated, the condenser coils 114, 124 are each split between the two slab portions 382, 386. That is, the first condenser coil 114 includes a first upstream coil portion 390 fluidly coupled in parallel with a second upstream coil portion 392. Additionally, the second condenser coil 124 includes a first downstream coil portion 394 fluidly coupled in parallel with a second downstream stream coil portion 396. As such, the first refrigerant 112 is directed from the first compressor 190 and splits to flow into the first and second upstream coil portions 390, 392 in parallel, while the second refrigerant 122 is directed from the second compressor 192 and splits to flow into the first and second downstream coil portions 394, 396 in parallel. Indeed, because the downstream coil portions 394, 396 are stacked on top of the upstream coil portions 390, 392, the serial condenser 104 includes a stacked arrangement for the coil portions 390, 392, 394, 396. The coil portions are referenced herein as upstream or downstream coil portions relative to the air flow 150 pulled or pushed across the serial condenser 104.

Thus, compared to a traditional condenser that may include the first condenser coil 114 and the second condenser coil 124 in series with one another, the first condenser coil 114 may receive the air flow 150 at the lower, ambient temperature to maintain a lower condensing temperature and increase the part-load operating efficiency of the first compressor 190, which is an IDV compressor having the IDVs 194 discussed above. The resulting increase in efficiency for the first refrigerant circuit 110 may outweigh any decrease in efficiency of the second refrigerant circuit 120, such that the overall temperature lift and corresponding coefficient of performance of the serial condenser 104 is improved.

Accordingly, the present disclosure is directed to a coil arrangement that leverages the IDV capability of a first compressor to improve an overall operating efficiency of the multiple refrigerant circuit system. The multiple refrigerant circuit system includes multiple refrigerant circuits, for which a first portion of the multiple refrigerant circuits has a greater number of compressors having intermediate discharge valves than a second portion of the multiple refrigerant circuits, and for which condensers of the first portion of the multiple refrigerant circuits are disposed upstream of condensers of the second portion of the multiple refrigerant circuits relative to air flow. Accordingly, an air inlet temperature of the air flow directed across the condensers is lower for the condensers of the first portion of the multiple refrigerant circuits, such that during part-load operation, the IDVs are actuated, and the efficiency of the condensers associated with the IDV capability is increased by a greater degree than any decrease in efficiency of the downstream condensers that are not associated with the IDV capability.

While only certain features and embodiments of the present disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, and so forth, without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the present disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode of carrying out the present disclosure, or those unrelated to enabling the claimed disclosure. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation. 

1. A multiple circuit refrigerant system, comprising: a first refrigerant circuit having a first condenser and a first compressor, wherein the first compressor is an intermediate discharge valve (IDV) compressor; and a second refrigerant circuit having a second condenser and a second compressor, wherein the second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser.
 2. The multiple circuit refrigerant system of claim 1, comprising a controller configured to actuate the first compressor in response to a request for part-load operation of the multiple circuit refrigerant system.
 3. The multiple circuit refrigerant system of claim 1, wherein the second compressor is a non-IDV compressor.
 4. The multiple circuit refrigerant system of claim 1, wherein the first refrigerant circuit comprises a greater quantity of IDV compressors than the second refrigerant circuit.
 5. The multiple circuit refrigerant system of claim 1, wherein the first refrigerant circuit and the second refrigerant circuit are equal in rated compressor tonnage.
 6. The multiple circuit refrigerant system of claim 1, wherein the first condenser is configured to operate at a first condensing temperature that is lower than a second condensing temperature of the second condenser, during part load operation of the multiple circuit refrigerant system.
 7. The multiple circuit refrigerant system of claim 1, wherein the first refrigerant circuit has a third compressor fluidly coupled to the first condenser, wherein the second refrigerant circuit has a fourth compressor fluidly coupled to the second condenser, and wherein the third compressor is an IDV compressor and the fourth compressor is an IDV compressor, the third compressor is an IDV compressor and the fourth compressor is a non-IDV compressor, or the third compressor is a non-IDV compressor and the fourth compressor is a non-IDV compressor.
 8. The multiple circuit refrigerant system of claim 1, wherein the first condenser and the second condenser are in a stacked arrangement.
 9. The multiple circuit refrigerant system of claim 8, wherein, in the stacked arrangement, the first condenser comprises a first outward-facing surface and a first inward-facing surface, the second condenser comprises a second outward-facing surface and a second inward-facing surface, and the first inward-facing surface faces the second inward-facing surface.
 10. The multiple circuit refrigerant system of claim 9, wherein the first inward-facing surface and the second inward-facing surface are in contact with one another.
 11. A multiple circuit refrigerant system, comprising: a first refrigerant circuit having a first condenser and a first compressor assembly fluidly coupled to the first condenser; and a second refrigerant circuit having a second condenser and a second compressor assembly fluidly coupled to the second condenser, wherein the second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser, and wherein the first compressor assembly comprises a greater quantity of intermediate discharge valve (IDV) compressors than the second compressor assembly.
 12. The multiple circuit refrigerant system of claim 11, wherein the second compressor assembly comprises a non-IDV compressor.
 13. The multiple circuit refrigerant system of claim 11, wherein the first compressor assembly comprises a first IDV compressor fluidly coupled with a second IDV compressor in parallel, and wherein the second compressor assembly comprises a first non-IDV compressor fluidly coupled in with a second non-IDV compressor in parallel.
 14. The multiple circuit refrigerant system of claim 11, wherein the first compressor assembly comprises a first IDV compressor fluidly coupled with a second IDV compressor in parallel, and wherein the second compressor assembly comprises a third IDV compressor fluidly coupled with a non-IDV compressor in parallel.
 15. The multiple circuit refrigerant system of claim 11, comprising a controller communicatively coupled to the first compressor assembly and the second compressor assembly, wherein the controller is configured to instruct the first compressor assembly, the second compressor assembly, or both to control a respective refrigerant flow through the first refrigerant circuit, the second refrigerant circuit, or both.
 16. The multiple circuit refrigerant system of claim 11, wherein the first refrigerant circuit and the second refrigerant circuit are fluidly independent from one another.
 17. The multiple circuit refrigerant system of claim 11, comprising a third refrigerant circuit having a third condenser and a third compressor assembly fluidly coupled to the third condenser, wherein the third condenser is disposed downstream of the second condenser relative to the air flow, and wherein the first compressor assembly comprises a greater quantity of IDV compressors than the third compressor assembly.
 18. The multiple circuit refrigerant system of claim 17, wherein the second compressor assembly comprises a same quantity of IDV compressors as the third compressor assembly.
 19. A multiple circuit refrigerant system, comprising: a first refrigerant circuit comprising a first condenser and a first compressor, wherein the first compressor is an intermediate discharge valve (IDV) compressor comprising an IDV; a second refrigerant circuit comprising a second condenser and a second compressor, wherein the second condenser is disposed downstream of the first condenser relative to an air flow directed across the first condenser and the second condenser; and a controller configured to actuate the first compressor in response to a request for part-load operation of the multiple circuit refrigerant system, wherein the first compressor is configured to actuate the IDV during the part-load operation of the multiple circuit refrigerant system.
 20. The multiple circuit refrigerant system of claim 19, wherein a cooling capacity demand associated with the part-load operation is greater than a cooling capacity of the first refrigerant circuit, and wherein the controller is configured to actuate the second compressor in response to the request for part-load operation of the multiple circuit refrigerant system.
 21. The multiple circuit refrigerant system of claim 20, wherein the first condenser is configured to operate at a lower condensing temperature than the second condenser during the part-load operation of the multiple circuit refrigerant system.
 22. The multiple circuit refrigerant system of claim 19, wherein the second compressor comprises a non-IDV compressor.
 23. The multiple circuit refrigerant system of claim 19, wherein the controller is configured to actuate the first compressor and the second compressor in response to a request for full-load operation of the multiple circuit refrigerant system. 